When the driven rotary element is bolted to the camshaft, the fastening pressure applied to the driven rotary element is increased because of a small contacting area between the camshaft and the driven rotary element. In general, an aluminum material of low rigidity is often used for manufacturing the driven rotary element, and thus the driven rotary element is easily deformed.
Under the circumstances, a connecting element is disposed between the driven rotary element and the camshaft. This increases the contacting area between the camshaft and the driven rotary element to reduce a pressing force exerted upon the driven rotary element per unit area, as a result of which the deformation of the driven rotary element can be prevented.
Various parts are manufactured in various component facilities and delivered to an assembly shop to assemble the driven rotary element to the camshaft. The driven rotary element, the driving rotary element and the connecting element of all the components are manufactured in the same component facility and delivered as an assembled unit. The connecting element is press-fitted to a recess formed in one side of the driven rotary element and delivered as an integrated unit. Such an integrated configuration advantageously alleviates the trouble in delivery and facilitates the assembling work of the camshaft.
On the other hand, when the connecting element is press-fitted to the recess of the driven rotary element, only the surface of the driven rotary element provided with the recess is enlarged in diameter, as a result of which the entire driven rotary element may disadvantageously be deformed outward of the surface in a direction opposite to the recess. As a measure for overcoming such a disadvantage, Japanese Unexamined Patent Application Publication No. 2006-183590 discloses a technique for forming a recess for receiving the connecting element press-fittingly in the driven rotary element and also forming a recess for receiving a bushing press-fittingly in the back side of the driven rotary element (see PTL 1). This balances the degrees of deformation in diameter in both the surfaces of the element and prevents the driven rotary element from deforming outward of the surface.